1. Technical Field
The disclosure relates to an imaging device for imaging an object to generate an imaging signal, a drive signal adjustment method that is performed by the imaging device, and an endoscope system.
2. Related Art
Conventionally, an endoscope system is used in the medical field for observing an organ of a subject such as a patient. The endoscope system includes an endoscope (scope) and a processing device (processor). The endoscope includes an insertion portion formed in a flexible elongated shape, a distal end of which is provided with an imaging sensor. The insertion portion is inserted into a body cavity of the subject. The processing device is coupled to the insertion portion via a cable and a connector to perform an image process on an in-vivo image captured by the imaging sensor. The processing device causes a display device to display the in-vivo image. For example, power or a signal is supplied from the processing device to the imaging sensor at the distal end of the insertion portion.
In recent years, application of an imaging sensor having a large number of pixels that enables the observation of a clearer image to the endoscope has been considered, and a small diameter of the insertion portion has been required in consideration of easiness of introduction of the endoscope into the subject. In order to realize a small diameter of the insertion portion, an inner transmission cable needs to be made thinner. When the transmission cable is made thinner, however, electric resistance of the transmission cable is increased, whereby an attenuation rate of a drive signal such as a power supply signal and a clock signal is increased. In addition, since the length and the thickness of the transmission cable vary in accordance with a kind of the endoscope, an attenuation amount of the drive signal changes depending on the endoscope. A value of the drive signal is conventionally set at a relatively high level so that the value can be applied to all kinds of endoscopes. However, exact adjustment of the value of the drive signal that depends on the endoscope has been required so as to be able to deal with prevention of heat generation due to a reduction in the voltage of the imaging sensor and an increase in speed of signal transmission.
In this regard, an endoscope system including a voltage detection unit has been proposed (for example, refer to JP 2009-106343 A). Specifically, the voltage detection unit that detects voltage values at two points including an imaging unit and a driver circuit is newly provided at a distal end of an insertion portion of an endoscope, and the voltage that is applied to the endoscope is adjusted on the basis of the voltage values detected in the voltage detection unit when power is supplied.